In the field of vertical sports, there are removable belay devices, notably of the ice screw type as shown in FIG. 1, comprising an elongated tubular shaft 1 with an external thread 2 and a bit 3 with teeth 4. Bit 3, shown in more detail in FIG. 2, is provided at a longitudinal end E11 of shaft 1. Each tooth 4 has a cutting edge 5. Opposite to bit 3, i.e. at the other longitudinal end E12 of shaft 1, a head 6 equipped with a fastening lug is fixedly joined to shaft 1. This fastening lug is typically used to form a securing point for a climber and to allow rotation to screw shaft 1 in ice.
Frequently, cutting edges 5 get blunt as bit 3 is used. In such case, a user may, as shown in FIG. 3, perform a maintenance step of his belay device using a sharpening file 7 to grind the edge of tooth 4 at its cutting edge 5. However, such a sharpening is not easy and requires some skill not to cut into shaft 1 of the device. Moreover, if shaft 1 is cut into during the sharpening, this may, in some extreme cases, damage the integrity of the device or its performances in use.
Further, the sharpening of the cutting edge oriented to face the screwing direction and that of another cutting edge of the tooth opposed to the preceding cutting edge, to delimit the top of the tooth, also allows to sharpen the top of the associated tooth in order to obtain a point.
EP 1491238 discloses an ice screw with a bit whose sharpening is complicated to perform.
SU 939891 relates to a tool for drilling a hole in ice. Such a tool does not have an elongated shaft with an external thread and is generally used by fishermen and not by mountaineers. It is to be noted that the tooth is not sharpened on the side. The sharpened area is at the bottom of the tooth.